Ditch the guy.
A guy who's questionable as a pledge will likely be a problem as a Brother. Get rid of him before you get initiated/installed. Don't let him poison the well.
Throw the guy out!!! There is no room for people like that in a chapter or colony!! He apparantly doesn't respect you or the colony or what it means to be a PIKE!!! So he should be kicked to the curb!!!
What kind of chapter is it that allows a pledge to do that to a brother and then tell him that his punishment is that he can't drink for a semester?
That's not brotherhood, not even close.